Hyper Threading
The amazing growth of the Internet and telecommunications is powered by ever-faster systems demanding increasingly higher levels of processor performance. To keep up with this demand, we cannot rely entirely on traditional approaches to processor design. Micro-architecture techniques used to achieve past processor performance improvement ? super-pipelining, branch prediction, super-scalar execution out-of-order execution, caches ? have made microprocessors increasingly more complex, have more transistors, and consume more power in fact transistor counts and power are increasing at rates greater than processor performance. Processor architects are therefore looking for ways to improve performance at a greater rate than transistor counts and power dissipation. Intel?s Hyper-Threading Technology is one solution.
What is Hyper-Threading Technology?
Hyper-threading Technology is a ground breaking innovation that significantly improves processor performance throughout the enterprise. Pioneered by Intel on the Intel Xeon processor family for server, Hyper-Threading Technology has enabled greater business productivity and enhanced the customer experience.
Hyper-Threading Technology is now supported on both the Intel Pentium 4 Processor with HT Technology for desktops and entry-level workstations, and notebooks with the Mobile Intel Pentium 4 processor supporting Hyper-Threading Technology. Hyper-Threading Technology provides a significant performance boost that is particularly suited to today?s business computing climate, applications, and operating systems.
Using this new technology, two separate threads can run simultaneously on one processor as long as thy don?t both require the same execution unit. The processor schedules the instructions of the two threads in interleaved fashion depending on which execution units are available. The two threads share the caches for data and instructions in all ways, this arrangement looks like two processors. However, there are some key distinctions the most important is that the threads rarely run at full speed. The interleaving almost certainly assures that there will be occasional collisions for resources. Hypothetical examples can be constructed where two threads do not ever interfere with each other, but they do performance approaches that of two a common scenario. In such cases performance approaches that of two separate processors. In tested applications, Intel has attributed performance enhancements of around 30% to hyper-threading technology.
Hyper-Threading Technology requires:
A computer system with an Intel Pentium 4 processor at 3.06 GHz or higher
A chipset and BIOS that utilize this technology.
An operating system that includes optimizations for this technology.
Performance will vary depending on the specific hardware and software you use.
How Hyper-Threading works?
Faster clock speeds are an important way to deliver more computing power, and Intel has led the way with industry-leading processor frequency. But clock speed is only half the story. The other route to higher performance is to accomplish more work on each clock cycle, and that?s where Hyper-Threading Technology comes in. A single processor supporting Hyper-Threading Technology presents itself to modern operating systems and applications as two virtual processors. The processor can work on two sets of tasks simultaneously use resources that otherwise would sit idle, and get more work done in the same amount of time.
In desktop and notebook PCs and entry-level workstations, HT Technology takes advantage of the multithreading capability that?s built in to windows XP and many advanced applications. Multithreaded software divides its workloads into processes and threads that can be independently scheduled and dispatched. In a multiprocessor system, those threads execute on different processors. HT Technology allows a single Pentium 4 Processor to function as two virtual or logical processors. There?s still just one physical Pentium 4 processor in your PC ? but the processor can execute two threads simultaneously.
In servers and high-performance workstations, Hyper-Threading Technology enables thread-level parallelism (TLP) by duplicating the architectural state on each processor while sharing one set of processor execution resources. When scheduling threads, the operating system treats the two distinct architectural states as separate ?logical? processors, which allows multiprocessor capable software to run unmodified on twice as many logical processors. Although Hyper-Threading Technology will not provide the level of performance scaling achieved by adding a second processor, benchmark tests show some server applications can experience a 30 percent gain in performance. While this technology can boost applications running an Microsoft Windows 00 Advanced Server, it will perform best with operating systems that have been optimized for operating systems that have been optimized for Hyper-Threading Technology, including Microsoft .Net Server, Windows XP, and certain versions of Linux. Performance and responsiveness.
Benefits of Hyper-Threading Technology include:
- High processor utilization rates: One processor with two architectural states enables the processor to more efficiently utilize execution resources. Because the two threads share one set if execution resources, the second thread can use resources that would be otherwise idle if only one thread was executing the result is an increased utilization of the execution resources within each physical processor package.
- Higher performance for properly optimized software: Greater throughput is achieved when software is multithreaded in a way that allows different threads to tap different processor resources in parallel. For example, integer operations are scheduled on one logical processor while floating-point computations occur on the other.
- Full backward compatibility: Virtually all multiprocessor-aware operating systems and multithreaded applications benefit from Hyper-Threading Technology. Software that lacks multiprocessor capability is unaffected by Hyper-Threading Technology.
Conclusion
Multiprocessing systems run threads on separate processors. Systems with Hyper-Threading Technology run two threads on one chip. The new Intel Xeon processor-based servers combine both technologies. They run two hyper-threading technology enabled processors on the same machine. This creates a machine with four concurrent threads executing. If the instructions are scheduled correctly ? and the operating systems are tuned for hyper-threading ? the machines get enormous processing capability, and thread-heavy applications like Java Virtual Machines run considerably faster.
